With technical advancements in communication terminals such as mobile phones, communication terminals having a positioning function using GPS (Global Positioning System) are becoming popular. When performing a positioning calculation using GPS with a communication terminal, with a single point positioning method in which positioning is performed by only receiving radio waves from a GPS satellite, there are concerns over an increase in positioning time, an increase in power consumption by the communication terminal, and the like. Therefore, a network-assisted method is adopted which reduces positioning time by transmitting acquisition information of a position of a GPS satellite or the like (assistance data) from a positioning support server to a communication terminal (for example, refer to Patent Document 1).
In addition, with GPS positioning by the network-assisted method described above, as information indicating a general position of a communication terminal (approximate positional information), information identifying a position of a base station of an area in which the communication terminal exists is transmitted from the positioning support server to the communication terminal as one type of assistance data. The approximate positional information of the communication terminal refers to information that contributes significantly to a success rate of GPS positioning.